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Total debt and equity financial instruments including: (1) securities held-to-maturity, (2) trading securities, and (3) securities available-for-sale.

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Investment And Other Gains Investment And Other Gains (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Marketable Securities, Realized Gain (Loss)	$ 0	$ 10,038
Proceeds from sales of marketable securities	$ 0	18,182	$ 18,182
2017 Sales Transaction [Member]
Proceeds from sales of marketable securities		$ 11,718
Marketable securities				$ 11,745
Available-for-sale Securities, Amortized Cost Basis				$ 1,680
2016 Sales Transaction [Member]
Proceeds from sales of marketable securities			$ 6,464